Domestic fowl eggs having a high content of highly unsaturated fatty acid, their production process and their use

ABSTRACT

The present invention provides domestic fowl eggs having a high content of arachidonic acid and optionally docosahexaenoic acid obtained by feeding egg-laying domestic fowls ω6 highly unsaturated fatty acids and optionally ω3 highly unsaturated fatty acids, their production process, a lipid that originates from them, and a food that contains said lipid.

TECHNICAL FIELD

The present invention relates to domestic fowl eggs having a highcontent of arachidonic acid and optionally docosahexaenoic acid, and aprocess for production thereof from egg-laying domestic fowls raised byfeeding ω6 highly unsaturated fatty acid and optionally ω3 highlyunsaturated fatty acid, as well as lipid having a high content ofarachidonic acid and optionally docosahexaenoic acid, obtained from saiddomestic fowl eggs, a process for production thereof, and their use.

BACKGROUND ART

Although eggs having a high degree of nutritional value and areexcellent foods that contain a good balance of nutrients, due to theirhigh cholesterol content, their consumption must be restricted. Inrecent years, research has therefore been conducted to introduce variousdrugs into eggs to inhibit increases in blood cholesterol levels, andnumerous research has been reported.

On the other hand, after it was reported that ω3 highly unsaturatedfatty acids contained in fish oil have an effect of lowering bloodcholesterol (Japanese Unexamined Patent Publication No. 54-154533), atechnology was developed in which large amounts of docosahexaenoic acidand eicosapentaenoic acid are introduced into the egg yolks of domesticfowl eggs by raising egg-laying domestic fowls on feed to which wasadded fish oil containing ω3 highly unsaturated fatty acids (JapaneseExamined Patent Publication No. 3-36493).

However, reports of substances having the effect of lowering bloodcholesterol were not limited to ω3 highly unsaturated fatty acid. Thiseffect is also observed in ω6 highly unsaturated fatty acids such asγ-linolenic acid (Agric. Biol. Chem., 50, 2483-2491 (1986)),dihomo-γ-linolenic acid and arachidonic acid (“Lipid Metabolism of LiverDisease”, Chugai Medical Co., Ltd., 1994, pp. 127-130). However, amethod of for increasing amounts of ω6 highly unsaturated fatty acids,and particularly arachidonic acid, in eggs has not yet been developed.Moreover, in recent years, questions have been raised regarding theratio of ω6 highly unsaturated fatty acids and ω3 highly unsaturatedfatty acids. Consequently, instead of the conventional technology forincreasing amount of eicosapentaenoic acid or docosahexaenoic acid inegg yolks, there has been a strong desire for a method of containing ω6highly unsaturated fatty acid and ω3 highly unsaturated fatty acid inegg yolks in a favorable balance.

In view of these circumstances, it is stated for the amounts of ingestedfatty acids in the section concerning ingestion of fatty acids in theNutritional Requirements of the Japanese (5th Revision) that,“Consistent opinions have not yet been obtained regarding the ratio ofingestion of n-6 (ω6) fatty acids and n-3 (ω3) fatty acids. The resultsof a nutritional survey of Japanese showed that many of those surveyedfatty acids are ingested in the ratio of roughly 4:1, and this ratio isconsidered to be suitable at the present stage.” (Ministry of Health andWelfare, Health Service Bureau, Health Promotion and Nutrition Dept.ed.: “Nutritional Requirements of the Japanese, 5th Revision”, 1stedition, 1994, pp. 56-58).

In addition, it has also been recently reported that arachidonic acidand docosahexaenoic acid are contained in mother's milk, and that theyare useful in the growth and development of infants (“Advances inPolyunsaturated Fatty Acid Research”, Elsevier Science Publishers, 1993,pp 261-264). Moreover, their importance has also been reported in theheight and brain development of the fetus (Proc. Natl. Acad. Sci. USA,90, 1073-1077 (1993), Lancet, 344, 1319-1322 (1994)).

With this in mind, attempts were made to add arachidonic acid anddocosahexaenoic acid, for which there are large differences in the fattyacid composition between mother's milk and infant formula, to infantformula. Although infant formula containing fish oil is currentlyavailable on the market for the purpose of adding docosahexaenoic acidto a infant formula, eicosapentaenoic acid contained in fish oil isinherently hardly contained at all in mother's milk. According to theresults of recent research, this substance is not always favorable forthe growth and development of premature infants (“Advances inPolyunsaturated Fatty Acid Research”, Elsevier Science Publishers, 1993,pp. 261-264). U.S. Pat. No. 5,374,657 describes an invention relating toan oil to be added to milk product for infants, which oil blendcomprises an edible oil in microbial cells containing docosahexaenoicacid and an edible oil in microbial cells containing arachidonic acid,but a small amount of eicosapentaenoic acid. However, since thisinvolves direct administration of microbiological oil to prematureinfants and nursing infants, considerable cautions are required in termsof safety.

On the other hand, U.S. Pat. No. 4,670,285 discloses an amount of fattyacids such as arachidonic acid required by infants, and a blend of eggyolk oil and vegetable oil as an edible fat product for incorporationinto an infant formula for providing these fatty acids. The egg yolklipid used here can be said to have a lower amount of eicosapentaenoicacid and be an extremely safe raw material in comparison with theabove-mentioned fish oil and microbial oil. However, since this egg yolklipid contains only small amounts of arachidonic acid anddocosahexaenoic acid (roughly 1.5% arachidonic acid and roughly 1.7%docosahexaenoic acid per the total fatty acids in the egg yolk lipid),it is uneconomical.

ω3 highly unsaturated fatty acids have an abundant supply source, namelyfish oil which have no problems whatsoever in terms of safety. However,there are surprisingly few supply sources of ω6 highly unsaturated fattyacids, such as arachidonic acid. For example, although it is known thatlarge amount of arachidonic acid are contained in liver, there are fewopportunities for its consumption as a food. In addition, it is presentonly in small amounts in other meats (roasts or filet portions).

Therefore, extensive efforts were made to seek a supply source of ω6highly unsaturated fatty acids such as arachidonic acid in the microbialworld. A technology was developed relating to the production of ω6highly unsaturated fatty acids by microorganisms represented by moldsbelonging to genus Mortierella, subgenus Mortierella (JapaneseUnexamined Patent Publication No. 63-044891). However, although thistechnology was considered to have a high degree of safety, it did notexpand significantly due to the problem of being of microbial origin.

Thus, there was a strong desire for the development of domestic fowleggs fortified with arachidonic acid and optionally docosahexaenoicacid, as well as a lipid having a high content of arachidonic acid, andoptionally docosahexaenoic acid extracted from those domestic fowl eggsfor use as safe sources of arachidonic acid.

DISCLOSURE OF THE INVENTION

Thus, the present invention provides domestic fowl eggs having a highcontent of arachidonic acid and optionally docosahexaenoic acid, and aprocess for production thereof, as well as a lipid having a high contentof arachidonic acid and optionally docosahexaenoic acid obtained fromsaid domestic fowl eggs, a process for production thereof and its use.

As a result of various research to achieve the above-mentioned object,the inventors of the present invention found that domestic fowl eggsobtained by feeding egg-laying domestic fowls with ω6 highly unsaturatedfatty acids and optionally ω3 highly unsaturated fatty acids have a highcontents of arachidonic acid and optionally docosahexaenoic acid, thatare at least 2%, respectively, of the total amount of fatty acids in theegg yolk, thereby leading to completion of the present invention.

Thus, the present invention provides domestic fowl eggs having a highcontent of arachidonic acid and optionally docosahexaenoic acid obtainedby feeding egg-laying domestic fowls with ω6 highly unsaturated fattyacid and optionally ω3 highly unsaturated fatty acid.

Moreover, the present invention provides a production process ofdomestic fowl eggs having a high content of arachidonic acid andoptionally docosahexaenoic acid comprising feeding egg-laying domesticfowls with ω6 highly unsaturated fatty acid and optionally ω3 highlyunsaturated fatty acid.

In addition, the present invention provides a lipid having a highcontent of arachidonic acid and optionally docosahexaenoic acid obtainedfrom domestic fowl eggs obtained by feeding egg-laying domestic fowlswith ω6 highly unsaturated fatty acid and optionally ω3 highlyunsaturated fatty acid.

Moreover, the present invention provides a production process of a lipidhaving a high content of arachidonic acid and optionally docosahexaenoicacid comprising extracting lipid having a high content of arachidonicacid and optionally docosahexaenoic acid from domestic fowl eggsobtained by feeding egg-laying domestic fowls with ω6 highly unsaturatedfatty acid and optionally ω3 highly unsaturated fatty acid.

Moreover, the present invention provides a food having arachidonic acidand optionally docosahexaenoic acid, containing at least 0.001% byweight of a lipid having a high content of arachidonic acid andoptionally docosahexaenoic acid obtained by extracting from domesticfowl eggs obtained by feeding egg-laying domestic fowls with ω6 highlyunsaturated fatty acid and optionally ω3 highly unsaturated fatty acid.

In a preferable embodiment of the above-mentioned invention, the ω6highly unsaturated fatty acid is at least one of the fatty acidsselected from the group consisting of γ-linolenic acid,dihomo-γ-linolenic acid and arachidonic acid. This is preferably used inat least one of the forms selected from the group consisting of freefatty acid, salt, ester, triacylglycerol, diacylglycerol,monoacylglycerol, glycerophospholipid, glyceroglycolipid,sphingophospholipid and sphingoglycolipid.

Preferably, ω6 highly unsaturated fatty acid is given to domestic fowlseither alone or as a mixture in the form of an oil or extract residueobtained by extracting from dried or wet microbial cells of amicroorganism having the ability to produce arachidonic acid, or driedor wet microbial cells of a microorganism having the ability to producearachidonic acid.

Microorganisms having the ability to produce arachidonic acid arepreferably of the genus Mortierella, Conidiobolus, Pythium,Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium, Aspergillus,Rhodotorula, Entomophthora, Echinosporangium and Saprolegnia.

Preferably, ω3 highly unsaturated fatty acid is at least one of thefatty acids selected from the group consisting of α-linolenic acid,8,11,14,17-eicosatetraenoic acid, 5,8,11,14,17-eicosapentaenoic acid,7,10,13,16,19-docosapentaenoic acid and 4,7,10,13,16,19-docosahexaenoicacid. These are preferably used in at least one of the forms selectedfrom the group consisting of free fatty acid, salt, ester,triacylglycerol, diacylglycerol, monoacylglycerol, glyerophospholipid,glyceroglycolipid, sphingophospholipid and sphingoglycolipid.

Preferably, ω3 highly unsaturated fatty acid is given to domestic fowlseither alone or as a mixture in the form of fish oil, fish powder, fishrefuse, fish oil extract, an oil or extract residue obtained byextracting from dried or wet microbial cells of a microorganism havingthe ability to produce docosahexaenoic acid, or dried or wet microbialcells of a microorganism having the ability to produce docosahexaenoicacid.

Microorganisms having the ability to produce docosahexanoic acid arepreferably of the genus Crypthecodimium, Isochrysis, Nanochloropsis,Chaetoceros, Phaeodactylum, Amphidinium, Gonyaulax, Peridimium,Chroomonas, Cryptomonas, Hemiselmis, Chilomonas, Chlorella,Histiobranchus, Coryphaenoides, Thraustchytrium, SchizochytriumConidiobolus and Entomorphthora.

DETAILED EXPLANATION

The present invention was completed on the basis of the above findings.Namely, the present invention relates to domestic fowl eggs having ahigh content of arachidonic acid and optionally docosahexaenoic acid,and a process for production thereof comprising feeding egg-layingdomestic fowls with ω6 highly unsaturated fatty acid and optionally ω3highly unsaturated fatty acid, as well as lipid having a high content ofarachidonic acid and optionally docosahexaenoic acid obtained byextracting from the resulting domestic fowl eggs, and particularly theyolks, a process for production thereof, and the use thereof.

The egg-laying domestic fowls used in the present invention may be anyof the large number of types of fowl referred to as poultry providedtheir eggs are edible, examples of which include chickens, quail, ducksand crossbreeds of wild and domestic ducks.

The ω6 highly unsaturated fatty acid of the present invention is thathaving at least 18 carbon atoms, preferably at least 20 carbon atoms,and at least 3 double bonds which start from the 6th carbon atomcounting from the carbon atom on the methyl group terminal of the fattyacid, examples of which include γ-linolenic acid, dihomo-γ-linolenicacid and arachidonic acid. Although these fatty acids can be used eitheralone or as a mixture, it is preferable that they include at leastarachidonic acid. In addition, these fatty acids can be added in variousforms. Examples of these forms include salts, atoxic metal salts, forexample, alkaline metal salts such as sodium salts and potassium salts,alkaline earth metal salts such as calcium salts and magnesium salts,ammonium salts, esters such as methylesters, ethylesters andpropylesters, triacylglycerols, diacylglycerols, monoacylglycerols,glyerophospholipids, glyceroglycolipids, sphingophospholipids andsphingoglycolipids.

The ω6 highly unsaturated fatty acids of the present invention may bechemically synthesized, or derived from an animal, plant ormicroorganism and so forth that contains ω6 highly unsaturated fattyacid, or that which is isolated, extracted, purified or is a residuethereof, an example of which is an oil or extract residue obtained froma microorganism having an ability to produce arachidonic acid. Inaddition, it is desirable that the oil containing ω6 highly unsaturatedfatty acid of the present invention contains at least 5.5%, preferablyat least 10%, and more preferably at least 20% arachidonic acid withrespect to total fatty acids.

Moreover, in the present invention, the ω6 highly unsaturated fatty acidcan be used in combination with other fatty acids such as linoleic acid,ω3 highly unsaturated fatty acids and so forth.

The ω3 highly unsaturated fatty acid has at least 18 carbon atoms and atleast 2 double bonds which start from the 3rd carbon atom counting fromthe carbon atom of the methyl group terminal of the fatty acid. Examplesof the ω3 highly unsaturated fatty acid used in the present inventionare α-linolenic acid, 8,11,14,17-eicosatetraenoic acid,5,8,11,14,17-eicosapentaenoic acid, 7,10,13,16,19-docosapentaenoic acidand 4,7,10,13,16,19-docosahexaenoic acid. For the sake of brevity, thedouble bond locations will be omitted. In addition, these fatty acidscan be added in various forms.

Examples of forms in which the above-mentioned fatty acids can be addedinclude salts, atoxic metal salts, for example, alkaline metal saltssuch as sodium salts and potassium salts, alkaline earth metal saltssuch as calcium salts and magnesium salts, ammonium salts, esters suchas methylesters, ethylesters and propylesters, triacylglycerols,diacylglycerols, monoacylglycerols, glycerophospholipids,glyceroglycolipids, sphingophospholipids and sphingoglycolipids.

The ω3 highly unsaturated fatty acids of the present invention may bechemically synthesized or derived from an animal, plant or microorganismand so forth that contains ω3 highly unsaturated fatty acid, or thatwhich is isolated, extracted or purified therefrom, examples of whichinclude fish oil, fish powder, fish refuse, fish oil extract, an oil orextract residue obtained from microorganisms having an ability toproduce docosahexanoic acid and so forth.

Typical examples of fish oils include sardine oil, herring oil, tunaoil, bonito oil, saury oil and menherden oil. Although there are noparticular limitations on the type of fish oil used in the presentinvention, since the fatty acid composition in the oil varies accordingto the type of fish, selecting and using a fish oil having a highcontent of docosahexaenoic acid and a low content of eicosapentaenoicacid is preferable for obtaining eggs having a low content ofeicosapentaenoic acid.

In the present invention, all microorganisms can be used provided theyhave an ability to produce arachidonic acid or docosahexaenoic acid.Examples of microorganisms having an ability to produce arachidonic acidinclude those of the genus Mortierella, Conidiobolus, Phythium,Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium, Aspergillus,Rhodotorula, Entomophthora, Echinosporangium and Saprolegnia.

In the case of the genus Mortierella, microorganisms belonging to thegenus Mortierella, subgenus Mortierella can be used, examples of whichinclude Mortierella elongata IFO 8570, Mortierella exiqua IFO 8571,Mortierella hygrophila IFO 5941 and Mortierella alpina IFO 8568. All ofthese strains can be acquired without restriction from the Institute forFermentation Osaka. In addition, the present inventions can also useMortierella elongata SAM 0219 (FERM P-8703) (FERM BP-1239).

Mortierella alpina is particularly preferable in the present inventionbecause it intracellularly accumulates a large amount of arachidonicacid. In addition, since this microorganism produces hardlyeicosapentaenoic acid at normal temperatures (preferably 20 to 30° C.),it is suited extremely well for obtaining eggs having a low content ofeicosapentaenoic acid. Examples of Mortierella alpina other than thatlisted above include Mortierella alpina ATCC 16266, ATCC 42430, ATCC32221, CBS219.35, CBS224.37, CBS250.53, CBS343.66, CBS527.72, CBS529.72,CBS608.70 and CBS754.68.

Examples of microorganisms that have an ability to producedocosahexaenoic acid include members of the phylum Chromophycota, suchas of the genus Crypthecodimium, Isochrysis, Nanochloropsis,Chaetoceros, Phaeodactylum, Amphidinium, Gonyaulax, Peridimium,Chroomonas, Cryptomonas, Hemiselmis, Chilomonas, as well as members ofthe phylum of Chlorophycota such as of the genus Chlorella,Histiobranchus, Coryphaenoides, Thraustchytrium, SchizochytriumConidiobolus and Entomorphthora. Examples of Crypthecodimium includeCrypthecodimium cohnii ATCC 30021, while examples of Thraustchytriuminclude Thraustchytrium aureum ATCC 34304. These strains can be acquiredwithout restriction from the American Type Culture Collection.

Microorganisms having an ability to produce arachidonic acid ormicroorganisms having an ability to produce docosahexaenoic acid can becultured in accordance with routine methods. For example, the spores,mycelia or pre-culture liquid obtained by culturing in advance of saidmicroorganism can be cultured by inoculating into liquid medium or solidmedium. An oil containing highly unsaturated fatty acid such asarachidonic acid or docosahexaenoic acid is intracellularly accumulatedas a result of culturing.

Following completion of culturing, cultured microbial cells are obtainedfrom the culture by commonly employed solid-liquid separation techniquessuch as centrifugal separation and filtration. Dry microbial cells areobtained by washing the cultured microbial cells with an ample amount ofwater and then drying. Drying can be performed by freeze-drying, spraydrying and so forth. The dried microbial cells are preferably extractedwith organic solvent in the presence of a nitrogen gas. Examples oforganic solvents that can be used include ethyl ether, hexane, methanol,ethanol, chloroform, dichloromethane, petroleum ether and acetone. Inaddition, favorable results can also be obtained by alternatingextraction with methanol and petroleum ether or by extraction using asingle-layer solvent of chloroform, methanol and water. An oil can thenbe obtained containing highly unsaturated fatty acid such as arachidonicacid or docosahexaenoic acid by distilling off the organic solvent fromthe extract under a reduced pressure.

According to the present invention, in the case of feeding domesticfowls with oil derived from microorganisms having an ability to producearachidonic acid or oil derived from microorganisms having an ability toproduce docosahexaenoic acid, in addition to the oil extracted fromcultured microbial cells, the oil can be fed in forms including cultureliquid taken during the course of culturing or that sterilized cultureliquid, culture liquid taken at completion of culturing or thatsterilized culture liquid, cultured microbial cells collected from thoserespective culture liquids or those dried microbial cells, or residueobtained after extracting oil from the microbial cells.

There are no particular limitations on the manner in which domesticfowls are fed with ω6 highly unsaturated fatty acid and optionally ω3highly unsaturated fatty acid. For example, these highly unsaturatedfatty acids can be added to feed, or given in drinking water followed byemulsification using O/W emulsifier, to a concentration of 0.1-3% byweight (Japanese Unexamined Patent Publication No. 60-105471) orsubcutaneously administered (Japanese Unexamined Patent Publication No.5-292583). In addition, in order to produce the domestic fowl eggs ofthe present invention, it is preferable to feed said domestic fowlswitht the fatty acids at a dose of at least 100 mg/day/fowl, andpreferably at least 400 mg/day/fowl. Although merely adding ω6 highlyunsaturated fatty acid and optionally ω3 highly unsaturated fatty acidin feed is the simplest method, since its oxidation cannot be avoided,there are problems in terms of its quality control as well as thegeneration of a foul odor in the vicinity of the breeding area.

However, in the case of using microorganisms that have an ability toproduce arachidonic acid or microorganisms that have an ability toproduce docosahexaenoic acid, although problems similar to those aboveoccur in the case of adding its extracted oil to feed, in the case ofusing the microbial cells of these microorganisms, the oil in themicrobial cells is stable and, there are immeasurable advantages interms of costs, since the extraction procedure can be omitted, as wellas in terms of being able to provide other nutrients (proteins, sugarsand so forth).

With the exception of trace amounts contained in the egg white and eggshell, virtually all of the lipid in domestic fowl eggs is contained inthe yolk, and the majority of this egg yolk lipid is said to be bound toprotein. Thus, in the case of extracting lipid from yolk, the amount andcomposition of the extracted lipid varies according to the type ofsolvent used and extraction conditions. If the egg yolk is treated inadvance using enzyme (protease preparation containing lipase), an amountof lipid extracted by solvent extraction increases. Examples oftypically used effective extraction agents include a mixture of ethanoland ether (3:1) and a mixture of chloroform and methanol (1:1), andthese solvents are suited for extraction of all yolk lipids. Inaddition, by first freeze-drying the yolk in advance to form a powder,and then extracting with a mixture of chloroform and methanol, lipid iscompletely extracted. In particular, ethanol or hexane alone, a mixtureof ethanol and hexane or a mixture of ethanol and water are preferablesince they are solvents suitable for use in foods.

Fatty acid analysis can be performed in accordance with routine methods.For example, fatty acids can be measured by gas chromatography,high-performance liquid chromatography and so forth.

The egg yolk lipid of the present invention thus obtained is richer inarachidonic acid than conventional eggs. More specifically, this eggyolk lipid contains at least 2%, preferably at least 2.7%, and morepreferably at least 3% arachidonic acid with respect to the total fattyacids contained in the egg yolk. In addition, in the present invention,fatty acid analysis of the resulting lipid having a high content ofarachidonic acid and docosahexaenoic acid indicates a ratio of 1 to 12parts by weight of docosahexaenoic acid to 1 to 12 parts by weight ofarachidonic acid. Moreover, said egg yolk lipid is characterized bydemonstrating a ratio of at least 5 parts by weight of arachidonic acidto 1 part by weight of eicosapentaenoic acid.

Therefore, the lipid of the present invention having a high content ofarachidonic acid and optionally docosahexaenoic acid extracted fromdomestic fowl eggs, and particularly the egg yolks, obtained by feedingegg-laying domestic fowls with ω6 highly unsaturated fatty acid andoptionally ω3 highly unsaturated fatty acid has a low ratio ofeicosahexaenoic acid with respect to total fatty acids in the egg yolkeven in the case the above-mentioned domestic fowls are raised usingfish oil for the ω3 highly unsaturated fatty acid. Thus, an extractedlipid is obtained that has high ratios of arachidonic acid andoptionally docosahexaenoic acid, which can be effectively used informula for premature infants, infant formula, a follow-up formula or asa milk product for expectance or nursing mother. Namely, a powderedformula that is closer to natural mother's milk can be obtained byadding an oil extracted from domestic fowl eggs, and particularly theyolks, obtained by feeding egg-laying domestic fowls with ω6 highlyunsaturated fatty acid and optionally ω3 highly unsaturated fatty acid,to the production process or finished formula such as dietary formula topremature infants, dietary formula to infants, a follow-up formula ormilk product for expectant nursing mothers.

The types of foods to which is added lipid having a high content ofarachidonic acid and optionally docosahexaenoic acid extracted fromdomestic fowl eggs of the present invention are not limited to formulafor premature infants, formula for nursing infants, follow-up formula ormilk product for expectant or nursing mothers. One example is theaddition to foods containing oils, examples of which include naturalfoods containing oils of meat, fish and nuts, foods to which oils areadded during preparation such as Chinese food, Chinese noodles and soup,foods using oil as a heat medium such as tempura, deep-fried fish,deep-fried bean curd, fried rice, doughnuts and deep-fried confections,oily foods or processed foods to which oils are added during processingsuch as butter, margarine, mayonnaise, salad dressing, chocolate,instant Chinese noodles, caramel, cookies and ice cream, as well asfoods that are sprayed or coated with oil during final processing suchas crackers, hard biscuits and jam-filled bread.

However, examples are not limited to foods containing oil, but ratheralso include agricultural foods such as bread, noodles, rice,confections, bean curd and their processed foods, fermented foods suchas rice wine and medicinal liquors, livestock foods such as sweet ricewine, vinegar, soy sauce, miso, salad dressing, yogurt, ham, bacon,sausage and mayonnaise, sea foods such as boiled fish paste, deep-friedfish and fish cake, as well as beverages such as fruit juice, softdrinks, sports drinks, alcoholic beverages and tea.

Although there are no particular limitations on the used amount of lipidhaving a high content of arachidonic acid and optionally docosahexaenoicacid extracted from domestic fowl eggs of the present invention, atleast 0.001% preferably at least 0.1%, and more preferably at least 1%by weight is contained with respect to the food product to which it isadded. The following provides a detailed explanation of the presentinvention through its embodiments.

EXAMPLES Example 1 Production of Arachidonic Acid Using MicroorganismsHaving Ability to Produce Arachidonic Acid

Using Mortierella alpina IFO 8568 for an arachidonic acid-producingmicroorganism, medium (1400 L) containing 2% glucose, 1% yeast extractand 0.1% soybean oil was placed in a 2000 L fermentor followed byaeration stirring culturing for 7 days under conditions of a temperatureof 28° C., aeration volume of 1.0 vvm and agitation of 80 rpm. Driedpowdered microbial cells were prepared following completion ofculturing. As a result, 26.7 kg of dried microbial cells were obtainedcontaining 60% oil having a high content of ω6 highly unsaturated fattyacids (3.0% γ-linolenic acid, 2.7% dihomo-γ-linolenic acid, 24.1%arachidonic acid (ω6 highly unsaturated fatty acids:ω3 highlyunsaturated fatty acids=29.8:1).

Example 2 Production of Docosahexaenoic Acid Using Microorganisms HavingAbility to Produce Docosahexaenoic Acid

Using Crypthecodimium cohnii ATCC30021 for docosahexaenoicacid-producing microorganism, 6.8 L of concentrated yeast extract (400g/l) and 12.5 L of glucose syrup (400 g/l) were added to artificialseawater culture liquid diluted to one-half concentration prepared bycombining 4.3 kg of I.O. and 230 L of tap water followed by culturingfor 76 hours under conditions of a temperature of 28° C., aerationvolume of 1.0 vvm and terminal speed of 73 cm/second. Followingcompletion of culturing, the algae cells were acquired by centrifugationand after washing the cells with water, were freeze-dried to preparedried microbial cells. As a result, microbial cells were obtainedcontaining 20% oil having a high content of ω3 highly unsaturated fattyacids (35.0% docosahexaenoic acid).

Example 3 Production of Eggs Having High Content of ω6 HighlyUnsaturated Fatty Acid (1)

Isa Brown, 200-day-old, egg-laying chickens were divided into two groupsof 30 chickens each. The first group was treated as the control groupand fed with ordinary feed for 33 days. The other group was treated asthe test group, namely the ω6 highly unsaturated fatty acid dose group,and fed with feed in which was mixed the dried microbial cells obtainedin Example 1 so that a total of 5 g were ingested daily (3 g as oilhaving a high content of ω6 highly unsaturated fatty acid).

The egg weight (g), yolk weight (g), yolk content (%), extracted oilweight (g), ratio of arachidonoic acid to total fatty acids (%), ratioof eicosapentaenoic acid to total fatty acids (%), and ratio ofdocosahexaenoic acid to total fatty acids (%) were determined for 3 eggsover time. Those results are shown in Table 1. Furthermore, the eggsthat were obtained were frozen, and after denaturing the protein, weredried at high frequency to form chips measuring 5-10 mm on a side(yield: 45%). 1000 ml of ethanol was added to 300 g of these chips,extracted for 2 hours at 60 to 70° C. and then filtered to obtain afiltrate. Moreover, 800 ml of ethanol was added to the filtrationresidue followed by additional extraction for 2 hours at 60 to 70° C.and filtration. The first and second filtrates were combined after whichthe ethanol was removed by a rotary evaporator (vacuum: 30 mmHg, 60-70°C.). Finally, molecular distillation was performed by circulating for 2hours at 60° C. and 10⁻³ mmHg to completely remove ethanol. 150 g ofyolk oil were obtained equal to roughly half of the 300 g of chips. Theratio of ω6 highly unsaturated fatty acids (and particularly arachidonicacid) to total lipid in the yolk was clearly increased by feeding thechickens with ω6 highly unsaturated fatty acids. Moreover, since ω3highly unsaturated fatty acids consisted almost entirely ofdocosahexaenoic acid, this oil is even more suitable in the case ofusing the extracted oil in powdered milk product for premature infantsand powdered milk product for nursing infants.

TABLE 1 No. of Days Group Item 0 5 10 16 20 25 30 33 Control Group Eggweight (3 eggs) g 201.4 195.8 198.8 204.1 211.0 199.4 213.1 210.4 Yolkweight g 49.6 50.1 51.2 52.7 53.9 50.3 55.1 51.4 Yolk content % 24.625.6 25.7 25.8 25.4 25.2 25.9 24.4 Extracted oil weight g 14.2 13.4 14.412.8 16.1 15.1 14.5 15.9 Arachidonic acid % 1.6 1.7 1.3 1.4 1.3 1.6 1.81.5 Eicosapentaenoic acid % trace trace trace trace trace trace tracetrace Docosahexaenoic acid % 1.7 1.5 1.6 1.8 1.7 1.7 1.5 1.8 Test GroupEgg weight (3 eggs) g 198.5 188.5 183.1 194.6 201.7 206.1 200.8 199.4Yolk weight g 48.3 47.1 45.7 47.6 49.8 52.6 50.3 49.9 Yolk content %24.3 25.0 25.0 24.5 24.7 25.5 25.0 25.0 Extracted oil weight g 13.7 14.716.1 13.1 14.4 15.8 14.3 13.8 Arachidonic acid % 1.7 2.4 3.6 3.9 4.0 3.74.3 3.6 Eicosapentaenoic acid % trace trace trace trace trace tracetrace trace Docosahexaenoic acid % 1.3 1.4 1.6 1.5 1.7 1.3 1.4 1.6

Example 4 Production of Eggs Having High Content of ω6 HighlyUnsaturated Fatty Acid (2)

Isa Brown, 200-day-old, egg-laying chickens were divided into two groupsof 30 chickens each. The first group was treated as the control groupand fed with ordinary feed for 33 days. The other group was treated asthe test group, namely the ω6 highly unsaturated fatty acid dose group.

The test group was fed for 33 days with a mixture of feed and driedmicrobial cells containing 60% of the oil having a high content of ω6highly unsaturated fatty acids (3.2% γ-linolenic acid, 4.4%dihomo-γ-linolenic acid, 39.0% arachidonic acid (ω6 highly unsaturatedfatty acids:ω3 highly unsaturated fatty acids=269.5:1)) obtained usingMortierella alpina CBS 210.32 as an arachidonic acid-producingmicroorganism in accordance with the production process of arachidonicacid using microorganisms described in Example 1, so that 5 g wereingested per day.

The egg weight (g), yolk weight (g), yolk content (%), extracted oilweight (g), ratio of arachidonic acid to total fatty acid (%), ratio ofeicosapentaenic acid to total fatty acid (%), and ratio ofdocosahexaenoic acid to total fatty acid (%) were determined for 3 eggsover time. Those results are shown in Table 2. Furthermore, yolk oil wasobtained using the same procedure as described in Example 3. The ratioof ω6 highly unsaturated fatty acids (and particularly arachidonic acid)to total lipid in the yolk was clearly increased by feeding the chickensω6 highly unsaturated fatty acid.

Moreover, since ω3 highly unsaturated fatty acids consisted almostentirely of docosahexaenoic acid, this oil is even more suitable in thecase of using the extracted oil in powdered milk product for prematureinfants and powdered milk product for nursing infants.

TABLE 2 No. of Days Group Item 0 5 10 16 20 25 30 33 Control Group Eggweight (3 eggs) g 201.4 195.8 198.8 204.1 211.0 199.4 213.1 210.4 Yolkweight g 49.6 50.1 51.2 52.7 53.9 50.3 55.1 51.4 Yolk content % 24.625.6 25.7 25.8 25.4 25.2 25.9 24.4 Extracted oil weight g 14.2 13.4 14.412.8 16.1 15.1 14.5 15.9 Arachidonic acid % 1.6 1.7 1.3 1.4 1.3 1.6 1.81.5 Eicosapentaenoic acid % trace trace trace trace trace trace tracetrace Docosahexaenoic acid % 1.7 1.5 1.6 1.8 1.7 1.7 1.5 1.8 Test GroupEgg weight (3 eggs) g 197.3 199.1 201.5 203.7 198.2 204.6 211.0 206.2Yolk weight g 48.5 49.2 51.4 52.3 50.9 53.5 52.0 53.2 Yolk content %25.1 26.3 27.0 26.2 26.1 25.3 24.9 25.7 Extracted oil weight g 14.2 15.214.8 14.1 13.8 14.8 15.9 14.7 Arachidonic acid % 0.7 2.1 7.9 8.1 8.0 8.28.3 8.1 Eicosapentaenoic acid % trace trace trace trace trace tracetrace trace Docosahexaenoic acid % 1.6 1.4 1.8 1.6 1.6 1.5 1.3 1.4

Example 5 Production of Eggs Having High Content of ω6 HighlyUnsaturated Fatty Acid and ω3 Highly Unsaturated Fatty Acid (1)

Isa Brown, 200-day-old, egg-laying chickens were divided into two groupsof 30 chickens each. The first group was treated as the control groupand fed with ordinary feed for 33 days. The other group was treated asthe test group, namely the ω6 highly unsaturated fatty acid and ω3highly unsaturated fatty acid dose group, and fed for 33 days with amixture of ordinary feed, the dried microbial cells obtained in Example1 and fish oil so as to ingest 5 g per day of the dried microbial cells(3 g as oil having a high content of ω6 highly unsaturated fatty acids)and 3 g per day of fish oil (trace α-linolenic acid, 4.1%docosapentaenoic acid, 4.8% eicosapentaenoic acid, 21.8% docosahexaenoicacid) (ω6 highly unsaturated fatty acids:ω3 highly unsaturated fattyacids=1:30.7).

The chicken body weight (g), yolk weight (g), yolk content (%),extracted oil weight (g), ratio of arachidonic acid to total fatty acid(%), ratio of eicosapentaenoic acid to total fatty acid (%), and ratioof docosahexaenoic acid to total fatty acid (%) were determined for 3eggs over time. Those results are shown in Table 3. Furthermore, yolkoil was obtained using the same procedure as described in Example 3. Theratio of ω6 highly unsaturated fatty acids (and particularly arachidonicacid) and ω3 highly unsaturated fatty acids (and particularlydocosahexaenoic acid) to total lipid in the yolk was clearly increasedby feeding the chickens with ω6 highly unsaturated fatty acids and ω3highly unsaturated fatty acids.

TABLE 3 No. of Days Group Item 0 5 10 16 20 25 30 33 Control Group Eggweight (3 eggs) g 201.4 195.8 198.8 204.1 211.0 199.4 213.1 210.4 Yolkweight g 49.6 50.1 51.2 52.7 53.9 50.3 55.1 51.4 Yolk content % 24.625.6 25.7 25.8 25.4 25.2 25.9 24.4 Extracted oil weight g 14.2 13.4 14.412.8 16.1 15.1 14.5 15.9 Arachidonic acid % 1.6 1.7 1.3 1.4 1.3 1.6 1.81.5 Eicosapentaenoic acid % trace trace trace trace trace trace tracetrace Docosahexaenoic acid % 1.7 1.5 1.6 1.8 1.7 1.7 1.5 1.8 Test GroupEgg weight (3 eggs) g 195.5 186.6 203.8 205.7 190.4 212.4 212.7 206.5Yolk weight g 49.9 51 52.2 49.2 50.4 56.6 52.3 51.7 Yolk content % 25.527.3 25.6 23.9 26.5 26.6 24.6 25 Extracted oil weight g 13.2 15.2 13.112.4 11.4 13.2 16.3 14.8 Arachidonic acid % 0.74 1.75 3.1 4.04 3.2 4.33.9 3.1 Eicosapentaenoic acid % trace trace trace trace trace tracetrace trace Docosahexaenoic acid % 1.3 2.1 3.4 3.6 4.3 3.8 4.2 4.1

Moreover, although a high proportion of eicosapentaenic acid iscontained in the fish oil, in the present Example in which fish oil isused for the ω3 highly unsaturated fatty acids, the ratio ofeicosapentaenic acid to total lipid in the yolk can be held to less thanthat of docosahexaenoic acid.

Example 6 Production of Eggs Having High Content of ω6 HighlyUnsaturated Fatty Acid and ω3 Highly Unsaturated Fatty Acid (2)

Isa Brown, 200-day-old, egg-laying chickens were divided into two groupsof 30 chickens each. The first group was treated as the control groupand fed with ordinary feed for 33 days. The other group was treated asthe test group, namely the ω6 highly unsaturated fatty acid and ω3highly unsaturated fatty acid dose group, and fed for 33 days with amixture of ordinary feed, the dried microbial cells obtained in Example1 and the dried microbial cells obtained in Example 2 so as to ingest 5g per day of the dried microbial cells of Example 1 (3 g as oil having ahigh content of ω6 highly unsaturated fatty acids) and 10 g per day ofthe dried microbial cells of Example 2 (2 g as oil having a high contentof ω3 highly unsaturated fatty acids).

The egg weight (g), yolk weight (g), yolk content (%), extracted oilweight (g), ratio of arachidonic acid to total fatty acid (%), ratio ofeicosapentaenoic acid to total fatty acid (%), and ratio ofdocosahexaenoic acid to total fatty acid (%) were determined for 3 eggsover time. Those results are shown in Table 4. Furthermore, yolk oil wasobtained using the same procedure as described in Example 3. The ratioof ω6 highly unsaturated fatty acids (and particularly arachidonic acid)and ω3 highly unsaturated fatty acids (and particularly docosahexaenoicacid) to total lipid in the yolk was clearly increased by feeding thechickens with ω6 highly unsaturated fatty acids and ω3 highlyunsaturated fatty acids.

TABLE 4 No. of Days Group Item 0 5 10 16 20 25 30 33 Control Group Eggweight (3 eggs) g 201.4 195.8 198.8 204.1 211.0 199.4 213.1 210.4 Yolkweight g 49.6 50.1 51.2 52.7 53.9 50.3 55.1 51.4 Yolk content % 24.625.6 25.7 25.8 25.4 25.2 25.9 24.4 Extracted oil weight g 14.2 13.4 14.412.8 16.1 15.1 14.5 15.9 Arachidonic acid % 1.6 1.7 1.3 1.4 1.3 1.6 1.81.5 Eicosapentaenoic acid % trace trace trace trace trace trace tracetrace Docosahexaenoic acid % 1.7 1.5 1.6 1.8 1.7 1.7 1.5 1.8 Test GroupEgg weight (3 eggs) g 190.5 195.8 201.9 210.3 198.7 197.5 207.5 212.4Yolk weight g 45.3 48.2 51.3 53.5 50.2 50.1 52.6 49.7 Yolk content %23.8 24.6 25.4 25.4 25.3 25.4 25.3 23.4 Extracted oil weight g 14.1 15.613.9 14.3 16.1 14.0 15.7 16.3 Arachidonic acid % 1.8 2.3 3.2 3.9 4.2 3.94.1 3.6 Eicosapentaenoic acid % trace trace trace trace trace tracetrace trace Docosahexaenoic acid % 1.5 1.9 3.3 4.1 3.9 4.2 4.0 3.6

Example 7 Production of Eggs Having High Content of ω6 HighlyUnsaturated Fatty Acid and ω3 Highly Unsaturated Fatty Acid (3)

Isa Brown, 200-day-old, egg-laying chickens were divided into two groupsof 30 chickens each. The first group was treated as the control groupand fed with ordinary feed for 33 days. The other group was treated asthe test group, namely the ω6 highly unsaturated fatty acid and ω3highly unsaturated fatty acid dose group.

The test group was fed for 33 days with a mixture of feed, driedmicrobial cells containing 60% oil having a high content of ω6 highlyunsaturated fatty acids (3.2% γ-linolenic acid, 4.4% dihomo-γ-linolenicacid, 39.0% arachidonic acid (ω6 highly unsaturated fatty acids:ω3highly unsaturated fatty acids=269.5:1)), obtained using Mortierellaalpina CBS 210.32 for the arachidonic acid-producing mold in accordancewith the production process of arachidonic acid using microorganismsdescribed in Example 1, and fish oil (trace α-linolenic acid, 4.1%docosapentaenoic acid, 4.8% eicosapentaenoic acid, 21.8% docosahexaenoicacid (ω6 highly unsaturated fatty acids:ω3 highly unsaturated fattyacids=1:30.7)) so that 5 g per day of the oil and 3 g per day of fishoil were ingested.

The egg weight (g), yolk weight (g), yolk content (%), extracted oilweight (g), ratio of arachidonoic acid to total fatty acid (%), ratio ofeicosapentaenoic acid to total fatty acid (%), and ratio ofdocosahexaenoic acid to total fatty acid (%) were determined for 3 eggsover time. Those results are shown in Table 5. Furthermore, yolk oil wasobtained using the same procedure as described in Example 3. The ratioof ω6 highly unsaturated fatty acids (and particularly arachidonic acid)and ω3 highly unsaturated fatty acids (and particularly docosahexaenoicacid) to total lipid in the yolk was clearly increased by feeding thechickens with ω6 highly unsaturated fatty acids and ω3 highlyunsaturated fatty acids.

Moreover, in the case of using fish oil for the ω3 highly unsaturatedfatty acids, although a high proportion of eicosapentaenic acid iscontained in the fish oil, when given as feed, hardly anyeicosapentaenic acid was contained in the egg yolks.

TABLE 5 No. of Days Group Item 0 5 10 16 20 25 30 33 Control Group Eggweight (3 eggs) g 201.4 195.8 198.8 204.1 211.0 199.4 213.1 210.4 Yolkweight g 49.6 50.1 51.2 52.7 53.9 50.3 55.1 51.4 Yolk content % 24.625.6 25.7 25.8 25.4 25.2 25.9 24.4 Extracted oil weight g 14.2 13.4 14.412.8 16.1 15.1 14.5 15.9 Arachidonic acid % 1.6 1.7 1.3 1.4 1.3 1.6 1.81.5 Eicosapentaenoic acid % trace trace trace trace trace trace tracetrace Docosahexaenoic acid % 1.7 1.5 1.6 1.8 1.7 1.7 1.5 1.8 Test GroupEgg weight (3 eggs) g 198.2 199.1 204.8 203.1 194.5 211.7 212.7 203.3Yolk weight g 49.9 51.2 52.4 49.3 50.1 54.4 52.3 53.5 Yolk content %24.8 26.6 27.1 25.9 25.4 26.6 24.8 25.9 Extracted oil weight g 14.3 15.514.8 13.9 12.7 13.2 15.9 14.8 Arachidonic acid % 0.7 2.2 8.0 8.1 8.1 8.28.2 8.3 Eicosapentaenoic acid % trace trace trace trace trace tracetrace trace Docosahexaenoic acid % 1.5 2.1 3.3 4.2 3.9 4.1 4.0 4.3

Example 8 Preparation of Formula Containing Oil Having a High Content ofArachidonic Acid

A formula suitable for feeding infants having a high content ofarachidonic acid was prepared by mixing 1 g of the oil having a highcontent of arachidonic acid obtained in Example 3 into 100 g of formulamaterial. The ratio of arachidonic acid to total fatty acids of thisformula was 0.16%, thus enabling the amount of arachidonic acid lackingin conventional infant formula to approach that of natural mother'smilk.

Example 9 Preparation of Formula Containing Oil Having High Content ofHighly Unsaturated Fatty Acid

A formula suitable for feeding infants having a high content ofarachidonic acid and docosahexaenoic acid was prepared by mixing 1 g ofthe oil having a high content of arachidonic acid and docosahexaenoicacid (4.0% arachidonic acid, trace eicosapentaenoic acid, 4.1%docosahexaenoic acid) obtained from eggs obtained in Example 5 into 100g of formula material. The ratios of arachidonic acid, eicosapentaenoicacid and docosahexaenoic acid to total fatty acids of this formulaproduct were 0.16%, trace, and 0.16%, respectively, thus enabling theamounts of arachidonic acid and docosahexaenoic acid lacking inconventional infant formula to approach those of natural mother's milk.

What is claimed is:
 1. Domestic fowl eggs having at least 3% arachidonicacid with respect to total fatty acids contained in an egg yolk andoptionally docosahexaenoic acid, wherein said domestic fowl eggs areobtained by feeding egg-laying domestic fowls with at least one ω6highly unsaturated fatty acid selected from the group consisting ofdihomo-γ-linolenic acid and arachidonic acid and optionally ω3 highlyunsaturated fatty acid.
 2. Domestic fowl eggs according to claim 1wherein the ω6 highly unsaturated fatty acid is at least one fatty acidselected from the group consisting, dihomo-γ-linolenic acid andarachidonic acid, that is used in at least one form selected from thegroup consisting of free fatty acid, salt, ester, triacylglycerol,diacylglycerol, monoacylglycerol, glycerophospholipid, glycerolycolipid,shingophospholipid and sphingoglycolipid.
 3. Domestic fowl eggsaccording to claim 1 obtained by feeding said ω6 highly unsaturatedfatty acid either alone or as a mixture in the form of (1) an oil orextract residue obtained by extracting from dried microbial cells or wetmicrobial cells of a microorganism having an ability to producearachidonic acid or (2) dried or wet microbial cells of a microorganismhaving an ability to produce arachidonic acid.
 4. Domestic fowl eggsaccording to claim 3 wherein the microorganism having an ability toproduce arachidonic acid is of the genus Mortierella, Conidiobolus,Pythium, Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium,Aspergillus, Rhodotorula, Entomophthora, Echinosporangium orSaprolegnia.
 5. Domestic fowl eggs according to claim 1 wherein the ω3highly unsaturated fatty acid is present and is at least one fatty acidselected from the group consisting of α-linolenic,8,11,14,17-eicosatetraenoic acid, eicosapentaenoic acid,docosapentaenoic acid and docosahexaenoic acid, that is used in at leastone form selected from the group consisting of free fatty acid, salt,ester, triacylglycerol, diacylglycerol, monoacylglycerol,glyerophospholipid, glyceroglycolipid, spingophospholipid andsphingoglycolipid.
 6. Domestic fowl eggs according to claim 1 obtainedby feeding said ω3 highly unsaturated fatty acid either alone or as amixture in the form of fish oil, fish powder, fish refuse, fish oilextract, an oil or extract residue obtained by extracting from dried orwet microbial cells of microorganism having the ability to producedocosahexaenoic acid, or dried or wet microbial cells of microorganismhaving the ability to produce docosahexaenoic acid.
 7. Domestic fowleggs according to claim 6 wherein the microorganism having the abilityto produce docosahexaenoic acid is of the genus Crypthecodimium,Isochrysis, Nanochloropsis, Chaetoceros, Phaeodactylum, Amphidinium,Gonyaulax, Peridimium, Chroomonas, Cryptomonas, Hemiselmis, Chilomonas,Chlorella, Histiobranchus, Coryphaenoides, Thraustchytrium,Schizochytrium, Conidiobolus or Entomorphthora.
 8. A production processof domestic fowl eggs having at least 3% arachidonic acid with respectto the total fatty acids contained in the egg yolk and optionallydocosahexaenoic acid comprising feeding egg-layer domestic fowls with atleast one ω6 highly unsaturated fatty acid selected from the groupconsisting of dihomo-γ-linolenic acid and arachidonic acid andoptionally ω3 highly unsaturated fatty acid.
 9. A process according toclaim 8 wherein the ω6 highly unsaturated fatty acid is at least onefatty acid selected from the group consisting of, dihomo-γ-linolenicacid and arachidonic acid, that is used in at least one form selectedfrom the group consisting of free fatty acid, salt, ester,triacylglycerol, diacylglycerol, monoacylglycerol, glycerophospholipidand sphingoglycolipid.
 10. A process according to claim 8 wherein the ω6highly unsaturated fatty acid is fed either alone or as a mixture in theform of (1) an oil or extract residue obtained by extracting from driedmicrobial cells or wet microbial cells of a microorganism having anability to produce arachidonic acid or (2) dried or wet microbial cellsof a microorganism having an ability to produce arachidonic acid.
 11. Aprocess according to claim 10 wherein said microorganism having theability to produce arachidonic acid is of the genus Mortierella,Conidiobolus, Pythium, Phytophthora, Penicillium, Cladosporium, Mucor,Fusarium, Aspergillus, Rhodotorula, Entomophthora, Echinosporangium orSaprolegnia.
 12. A process according to claim 8 wherein the ω3 highlyunsaturated fatty acid is present and is at least one fatty acidselected from the group consisting of α-linolenic acid,8,11,14,17-eicosatetraenoic acid, eicosapentaenoic acid,docosapentaenoic acid and docosahexaenoic acid, that is used in at leastone form selected from the group consisting of free fatty acid, salt,ester, triacylglycerol, diacylglycerol, monoacylglycerol,glyerosphospholipid, glyceroglycolipid, sphingophospholipid andsphingoglycolipid.
 13. A process according to claim 8 wherein the ω3highly unsaturated fatty acid is fed either alone or as a mixture in theform of fish oil, fish powder, fish refuse, fish oil extract, an oil orextract residue obtained by extracting from dried or wet microbial cellsof microorganism having the ability to produce docosahexaenoic acid, ordried or wet microbial cells of microorganism having the ability toproduce docosahexaenoic acid.
 14. A process according to claim 13wherein the microorganism having the ability to produce docosahexaenoicacid is of the genus Crypthecodimium, Isochrysis, Nanochloropsis,Chaetoceros, Phaeodactylum, Amphidinium, Gonyaulax, Peridimium,Chroomonas, Cryptomonas, Hemiselmis, Chilomonas, Chlorella,Histiobranchus, Coryphaenoides, Thraustchytrium, Schizochytrium,Conidiobolus or Entomorphthora.
 15. An egg yolk lipid having at least 3%arachidonic acid with respect to total fatty acids contained in the eggyolk lipid and optionally docosahexaenoic acid, wherein the egg yolklipid is obtained from domestic fowl eggs obtained by feeding egg-layingdomestic fowls with at least one ω6 highly unsaturated fatty acidselected from the group consisting of dihomo-γ-linolenic acid andarachidonic acid and optionally ω3 highly unsaturated fatty acid.
 16. Alipid according to claim 15 wherein the ω6 highly unsaturated fatty acidis at least one fatty acid selected from the group consisting of,dihomo-γ-linolenic acid and arachidonic acid, that is used in at leastone form selected from the group consisting of free fatty acid, salt,ester, triacylglycerol, diacylglycerol, monoacylglycerol,glycerophospholipid, glyceroglycolipid, sphingophospholipid andsphingoglycolipid.
 17. A lipid according to claim 15 obtained fromdomestic fowl eggs obtained by feeding said ω6 highly unsaturated fattyacid either alone or as a mixture in the form of (1) an oil or extractresidue obtained by extracting from dried microbial cells or wetmicrobial cells of a microorganism having an ability to producearachidonic acid or (2) dried or wet microbial cells of a microorganismhaving an ability to produce arachidonic acid.
 18. A lipid according toclaim 17 wherein the microorganism having the ability to producearachidonic acid is of the genus Mortierella, Conidiobolus, Pythium,Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium, Aspergillus,Rhodotorula, Entomophthora, Echinosporangium or Saprolegnia.
 19. A lipidaccording to claim 15 wherein the ω3 high unsaturated fatty acid ispresent and is at least one fatty acid selected from the groupconsisting of α-linolenic acid, 8,11,14,17-eicosatetraenoic acid,eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid,that is used in at least one form selected from the group consisting offree fatty acid, salt, ester, triacylglycerol, diacylglycerol,monocylglycerol, glyerophospholipid, glyceroglycolipid,sphingophospholipid and sphingoglycolipid.
 20. A lipid according toclaim 15 obtained from domestic fowl eggs obtained by feeding said ω3highly unsaturated fatty acid either alone or as a mixture in the formof fish oil, fish powder, fish refuse, fish oil extract, an oil orextract residue obtained by extracting from dried or wet microbial cellsof microorganism having the ability to produce docosahexaenoic acid, ordried or wet microbial cells of microorganism having the ability toproduce docosahexaenoic acid.
 21. A lipid according to claim 20 whereinthe microorganism having the ability to produce docosahexaenoic acid isof the genus Crypthecodimium, Isochrysis, Nanochloropsis, Chaetoceros,Phaeodactylum, Amphidinium, Gonyaulax, Peridimium, Chroomonas,Cryptomonas, Hemiselmis, Chilomonas, Chlorella, Histiobranchus,Coryphaenoides, Thraustchytrium, Schizochytrium, Conidiobolus orEntomorphthora.
 22. A lipid according to claim 15 that exhibits a ratioof 1 to 12 parts by weight of docosahexaenoic acid to 1 to 12 parts byweight of arachidonic acid, and exhibits a ratio of at least 5 parts byweight of arachidonic acid to 1 part by weight of eicosapentaenoic acid.23. A process for producing an egg yolk lipid having at least 3%arachidonic acid with respect to total fatty acids contained in the eggyolk lipid and optionally docosahexaenoic acid, said process comprisingextracting said egg yolk lipid from domestic fowl eggs obtained byfeeding egg laying domestic fowls with at least one ω6 highlyunsaturated fatty acid selected from the group consisting ofdihomo-γ-linolenic acid and arachidonic acid and optionally ω3 highlyunsaturated fatty acid.
 24. A process according to claim 23 wherein theω6 highly unsaturated fatty acid is at least one fatty acid selectedfrom the group consisting of, dihomo-γ-linolenic acid and arachidonicacid, that is used in at least one form selected from the groupconsisting of free fatty acid, salt, ester, triacylglycerol,diacylglycerol, monoacylglycerol, glycerophospholipid,glyceroglycolipid, sphingophospholipid and sphingoglycolipid.
 25. Aprocess according to claim 23 wherein the lipid is extracted fromdomestic fowl eggs obtained by feeding said ω6 highly unsaturated fattyacid either alone or as a mixture in the form of (1) an oil or extractresidue obtained by extracting from dried microbial cells or wetmicrobial cells of a microorganism having an ability to producearachidonic acid or (2) dried or wet microbial cells of a microorganismhaving an ability to produce arachidonic acid.
 26. A process accordingto claim 25 wherein the microorganism having the ability to producearachidonic acid is of the genus Mortierella, Conidiobolus, Pythium,Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium, Aspergillus,Rhodotorula, Entomophthora, Echinosporangium or Saprolegnia.
 27. Aprocess according to claim 23 wherein the ω3 highly unsaturated fattyacid is present and is at least one fatty acid selected from the groupconsisting of α-linolenic acid, 8,11,14,17-eicosatetraenoic acid,eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid,that is used in at least one form selected from the group consisting offree fatty acid, salt, ester, triacylglycerol, diacylglycerol,monoacylglycerol, glyerophospholipid, glyceroglycolipid,sphingophopholipid and sphingoglycolipid.
 28. A process according toclaim 23 wherein the lipid is extracted from domestic fowl eggs obtainedby feeding said ω3 highly unsaturated fatty acid either alone or as amixture in the form of fish oil, fish powder, fish refuse, fish oilextract, an oil or extract residue obtained by extracting from dried orwet microbial cells of microorganism having the ability to producedocosahexaenoic acid, or dried or wet microbial cells of microorganismhaving the ability to produce docosahexaenoic acid.
 29. A processaccording to claim 28 wherein the microorganisms having the ability toproduce docosahexaenoic acid is of the genus Crypthecodimium,Isochrysis, Nanochlorolsis, Chaetoceros, Phaeodactylum, Amphidinium,Gonyaulax, Peridimium, Chroomonas, Cryptomonas, Hemiselmis, Chilomonas,Chlorella, Histiobranchus, Coryphaenoides, Thraustchytrium,Schizochytrium, Conidiobolus or Entomorphthora.
 30. A process accordingto claim 23 comprising extracting a lipid exhibiting a ratio of 1 to 12parts by weight of docosahexaenoic acid to 1 to 12 parts by weight ofarachidonic acid, and exhibiting a ratio of at least 5 parts by weightof arachidonic acid to 1 part by weight of eicosapentaenoic acid.
 31. Afood having arachidonic acid and optionally docosahexaenoic acidcomprising at least 0.001% by weight of an egg yolk lipid having atleast 3% arachidonic acid with respect to the total fatty acidscontained in the egg yolk lipid and optionally docosahexaenoic acid,wherein said food is obtained by adding to a food an egg yolk lipid,wherein said egg yolk lipid is extracted from domestic fowl eggsobtained by feeding egg-laying domestic fowls with at least one ω6highly unsaturated fatty acid selected from the group consisting ofdihomo-γ-linolenic acid and arachidonic acid and optionally ω3 highlyunsaturated fatty acid.
 32. A food according to claim 31 wherein the ω6highly unsaturated fatty acid is at least one fatty acid selected fromthe group consisting of, dihomo-γ-linolenic acid and arachidonic acid,that is used in at least one form selected from the group consisting offree fatty acid, salt, ester, triacylglycerol, diacylglycerol,monoacylglycerol, glycerophospholipid, glyceroglycolipid,sphingophospholipid and sphingoglycolipid.
 33. A food according to claim31 obtained by adding a lipid having at least 3% arachidonic acid withrespect to total fatty acids contained in the lipid, wherein the lipidis obtained from domestic fowl eggs obtained by feeding said ω6 highlyunsaturated fatty acid either alone or as a mixture in the form of (1)an oil or extract residue obtained by extracting from dried microbialcells or wet microbial cells of microorganism having an ability toproduce arachidonic acid or (2) dried or wet microbial cells ofmicroorganism having an ability to produce arachidonic acid.
 34. A foodaccording to claim 33 wherein the microorganisms having the ability toproduce arachidonic acid is of the genus Mortierella, Conidiobolus,Pythium, Phytophthora, Penicillium, Cladosporium, Mucor, Fusarium,Aspergillus, Rhodotorula, Entomophthora, Echinosporangium orSaprolegnia.
 35. A food according to claim 31 wherein the ω3 highlyunsaturated fatty acid is present and is at least one of the fatty acidsselected from the group consisting of α-linolenic acid,8,11,14,17-eicosatetraenoic acid, eicosapentaenoic acid,docosapentaenoic acid and docosahexaenoic acid, that is used in at leastone form selected from the group consisting of free fatty acid, salt,ester, triacylglycerol diacylglycerol, monocylglycerol,glyerophospholipid, glyceroglycolipid, sphingophospholipid andsphingoglycolipid.
 36. A food according to claim 31 obtained by adding alipid having a ratio of 1 to 12 parts by weight of docosaphexaenoic acidto 1 to 12 parts by weight of arachidonic acid obtained from domesticfowl eggs obtained by feeding said ω3 highly unsaturated fatty acideither alone or as a mixture in the form of fish oil, fish powder, fishrefuse, fish oil extract, an oil or extract residue obtained byextracting from dried or wet microbial cells of microorganism having theability to produce docosaphexaenoic acid, or dried or wet microbialcells of microorganism having the ability to produce docosahexaenoicacid.
 37. A food according to claim 36 wherein said microorganism havingthe ability to produce docosahexaenoic acid is of the genusCrypthecodimium, Isochrysis, Nanochloropsis, Chaetoceros, Phaeodactylum,Amphidinium, Gonyaulax, Peridimium, Chroomonas, Cryptomonas, Hemiselmis,Chilomonas, Chlorella, Histiobranchus, Coryphaenoides, Thraustchytrium,Schizochytrium, Conidiobolus or Entomorphthora.
 38. A food according toclaim 31 wherein said food is a formula suitable for feeding prematureinfants, formula suitable for feeding infants, a follow-up formula or